1. Field of the Invention
The invention relates generally to the field of electronics. More particularly, the invention relates to voltage regulation.
2. Discussion of the Related Art
In battery operated devices, power consumption is a crucial design consideration. Because such devices are typically kept on inactive mode (sleep or standby) for long periods of time, it is important that power consumption be minimized during inactivity. Unfortunately, even where there is little processor action, sub-micron integrated circuits (ICs) may still consume considerable amounts of electrical current due in part to transistor leakage.
As IC technology moves towards deep sub-micron dimensions, leakage power (consumed during device inactivity) can become comparable to dynamic power (consumed during device activity). For example, if a circuit contains 50 million transistors and each transistor leaks around 1 nanoampere in the “off” mode, then the total leakage current for that circuit is of approximately 50 milliampere, which is unacceptable for most battery powered wireless applications.
One solution to this problem includes removing the power supply to the circuit when in the inactive mode. However, removing the supply to an entire circuit may cause some important information to be lost. This information is typically stored in elements such as latches and/or flip-flops, and it is required for quick recovery when the device becomes active again (wake-up).
Another solution to this problem includes power gating. In power gating, certain functional blocks of the IC are turned off during inactivity (regular cells), while others are kept on (keeper cells). Because keeper cells need only to retain their states and do not draw much current from the power supply, power gating may be achieved with the use of two distinct voltage regulators. However, use of a second regulator makes this a costly solution, taking up more area and requiring at least one extra external pin.